1. Field of the Invention
This invention relates to a system for detecting a flat portion of a peripheral surface of a vehicle wheel disposed in rolling engagement with a track rail.
2. Prior Art
When a railway vehicle or the like is braked intensely, a rotational speed of the braked wheel becomes lower than the speed of running of the vehicle, so that the braked wheel slides over the rail. When this sliding is excessive, the braked wheel is often prevented from rotating during the running of the vehicle. This phenomenon is commonly referred to as "adhesion" in the trade. As a result, a portion of the peripheral surface of the braked wheel is subjected to wear due to the friction between the braked wheel and the rail with which it is disposed in rolling engagement, thereby producing a flat portion on the peripheral surface of the braked wheel. When such a flat portion develops on the peripheral surface of the wheel, naturally the wheel can not be rotated smoothly, and this gives a rough ride. And, in some cases, a chassis of the vehicle may be subjected to damage. Further, noises caused by the flat portion of the rotating wheel may constitute a factor for a noise pollution. Generally, in order to overcome this difficulty, a railway train has heretofore been equipped with a detector for detecting the sliding of a wheel. When the detector detects the sliding of the wheel over the rail, the braking of the wheel is weakened so as to prevent the above-mentioned adhesion. Actually, however, even if the braking is weakened when the sliding of the wheel is detected, the adhesion may still develop when the friction between the wheel and the rail is low because the residual pressure of an associated braking device still applies a braking action to the wheel. Thus, the formation of the flat portion on the wheel can not be eliminated satisfactorily.